Fluid blast arc extinguishing circuit breaker



A. E. BROCK FLUID BLAST ARC EXTINGUISHING CIRCUIT B REAKR Filed Aug. 27,1945 'Y oct. 26, 194s.

INVENTOR. ARNOLD EBRO cx. BY

Patented Oct. 26, 1.948

'UNITED STATELS PATENT OFFICE FLUID BLAST ARC EXTINGUISHING CXRCUITBREAKER fornia Application August 2'?, 1945, Serial N0. 612,777

(Cl. 20S-148) 7 Claims. l

My present invention relates to high voltage circuit breakers, and moreparticularly to an improved means by which an arc drawn between thecircuit controlling contacts of the circuit breaker may be effectivelyinterrupted, irrespective of its current value, by a blast of air orother arc extinguishing fluid and it has for its object to provide animproved are extinguishing means for circuit breakers of the iiuid blasttype by which an arc established between the circuit interruptingcontacts of the circuit breaker may be effectively and eicientlyextinguished, irrespective of its current value, with a minimum of arcextinguishing uid.

Another object of the invention is to provide an improvement in circuitbreakers of the iiuid blast typewhich will prevent the building up of aback pressure by the generation of gases in an arc at the point ofcontact separation.

Another object of the invention is to provide i? an arc extinguishingdevice for use with the circuit controlling contacts of a fluid blastcircuit breaker in which means are provided for the venting of anyexcessive gas pressure that might interfere with the extinction of anarc therebetween at the time of circuit interruption.

A further object of the invention is to provide a new and novel contactarrangement for circuit breakers of. the axial blast arc extinguishingtype in which one of the contacts is provided with a pressure responsiveby-pass or valve means that will operate in the event of a sustained arcto relieve any excessive pressure caused by arc generated gases andpermit a substantially normal flow of arc extinguishing iluid throughthe arc at the time of circuit interruption.

Other objects and advantages of the invention will be evident to thoseskilled in the art, and pointed out hereinafter in the followingdescription taken in connection with the accompanying drawing, whereinthere is shown by way of illustration and not of limitation preferredembodiments of my invention.

In the drawing;

Figure 1 is a fragmentary vertical elevation showing my invention asapplied to a circuit breaker of the type employing the so-called axialblast principle for the extinction of any arc established between itscontacts upon circuit interruption,

Figure 2 `is a'fragmentar-y sectional view taken along'line II-'II ofFigure 1, looking in direction of arrows,

Figure 3 is a similar fragmentary sectional View taken along lineIII-III of Figure 1,

Figure l is a fragmentary sectional view showing a modified form or theinvention as applied to a circuit breaker of the type employing thesocalled transverse blast principle for `the extinction ci any arcestablished between the contacts thereof, and

Figure 5 is a fragmentary sectional view taken along line V-V of Figure4, looking in direction ci arrows.

rEhe use of a blast of air or other fluid as an arc extinguishing mediumin circuit breakershas long been considered, but up to the present timeno satisfactory arrangement has been found that will operatesuccessfully under all the various current values at which interruptionof a circuit may be necessary. This is believed to be due to the factthat once the circuit breaker has been designed, the physical dimensionsof the chamber surrounding the zone of arc interruption become fixed,while at the same time the current values of the arc to be extinguishedmay vary greatly. in other words, in the prior arrangements the blastsof arc extinguishing fluid employed operate in a substantially uniformmanner under all conditions and do not take into account the possiblevariations in the current values of the arc. As a result, at low currentvalues the blastvof arc extinguishing iuid or air is only slightlyheated and there is, therefore, establisheda low pressure area behindthe point of arcing between the separating contacts, which hinders arcinterruption. This low pressure area also tends to promote-a restriklngof the arc, due to the fact that it does not permit the building up ofsuiilcient dielectric effect within the blast of arc extinguishing fluidto extinguish the arc. Similarly, when an arc or" high current value isinterrupted, the arc extinguishing gases are heated to a highertemperature and expand to such an extent that there is orten establisheda reversal of now of arc extinguishing gases between the separatingcontacts. This retards the biast of arc extinguishing iiuid and resultsin a high ionisation thereof which likewise prevents arc extinctionandthe ultimate interruption of the circuit.

in view of the above, it `has been necessary in the past to compromisebetween the different op erating conditions that result from theinterruption of a circuit at diilerent current values. In this directiontwo methods have been used. The rst has been to provide a large volumebiast passageway in which the arc is drawn, and the second has been toconne the arc in a restricted chamber having a relatively narrowpassageway and provide a large exhaust outlet at or immediately beyondthe point of arcing. The first of these methods requires the use ofexcessive quantities of arc extinguishing fluid, and while the lattermeth-od is more economical in the use of the arc extinguishing fluid andhas met with some success, it is still open to the objection that ablocking pressure is often built up within the restricted passageway atthe point of contact separation that seriously interferes with the freenew of the arc extinguishing fluid through the passageway, which tendsto decrease the ecency oi the circuit breaker and lower its maximumcurrent interrupting capacity.

In accordance with the present invention, I provide an arc extinguishingarrangement in which the establishment of such a blocking pressure bythe arc generated gases is avoided, and in which a blast of arcextinguishing fiuid, having a substantially constant pressure andvelocity, may be used at all times regardless of the current value atthe time of the circuit interruption. This enables the use of a smallvolume of the arc extinguishing fluid and also avoids the need for acompromise in performance to meet different conditions oi current valueat the time of circuit interruption. This operation, with a constantpressure and velocity, regardless of current value at the time ofinterruption, is ob-ained in accoi-dance with the preferred embodimentof the invention by providing a fluid blast passageway which isexpandable, or in which the velocity and/ or volume of are extinguishingfluid flowing therethrough may vary in response to gas pressures thatmay result from temperature changes caused by the arc between theseparating contacts during circuit interruption.k It has been found tobe a fact that the interrupting capacity of circuit breakers employingan arc extinguishing fluid blast for interrupting an arc between itscontacts is limited by any condition that will permit the generation ofexcessive heat in an arc drawn between its separating contacts, whichwill result in a reverse flow of the arc extinguishing fluid through itsarc extinguishing chamber. This is true even though the reversal of ilowof the arc extinguishing iiuid may be only temporary, and often theinterrupting capacity or" the circuit breaker is limited to a value farbelow the maximum rated capacity thereof. This is explained by the factthat any reversal of flow or blocking pressure that will interfere withthe normal blast of the arc extinguishing iiuid through the arc willprevent a proper cooling of the highly ionized gases that are generatedin any arc drawn between the separating contacts when a circuit is beinginterrupted.

In the accompanying drawing, I have shown preferred arrangements,wherein the circuit controlling contacts of a circuit breaker aredisposed in arc extinguishing chambers that are provided with pressureresponsive or valved relief outlets through which the fluid blast and/orarc generated gas pressure may escape from the zone of arcing and thusprevent the building up of any blocking pressure within the contactenclosing chamber, which might interfere with a normal flow of the arcextinguishing fluid between the separating contacts.

In Figures 1, 2 and 3 of the drawing there is shown, in detail, anembodiment of the invention as applied to a circuit breaker of theso-called axial blast type. In circuit breakers of the axial iiow uidblast type the arc extinguishing luid introduced either through one ofthe contacts to the arcing space formed therebetween upon contactseparation, or the arc extinguishing fluid is charged into a chambersurrounding the separable contacts, so that when the contacts separate,this arc extinguishing fluid may exhaust under pressure axially outwardthrough one of the contacts. The device here shown is of this lattertype and, in its preferred form, it contemplates the employment of asubstantially cylindrical stationary Contact Ii? with which an axiallymovable contact II cooperates. The stationary contact III has atruncated conical contact surface I 2 at its inner end with which aconical contact surface I3, formed upon the contact I I, cooperates. Inthis way there is provided a restricted throat Ill at the inner end ofthe contact Iii through which an arc extinguishing fluid may dischargeoutwardly through the stationary Contact Id. As here shown, the contactsi!) and II are enclosed within a fluid pressure containing,- chamber I5that is formed thereabout by a tubular member It which carries suitableend closure members II. Only one of the end forming members II is hereshown, but it will be understood that a similar end closure member I'I,at the lower end of the chamber I5, will be provided with a packing orstuihng box through which the operating rod or shank of the movablecontactl il may move in a sealed manner. The stationary contact I0 ismounted within the chamber I5 and is secured to the closure member I' bymeans of an externally threaded bushing I8 that has a somewhat largerdischarge conduit located in alignment with the restricted throat lli atthe inner end of the contact I0. This bushing I8 extends through the endclosure member il and is secured by means of a threaded conduit formingmember i9 which may lead tothe atmosphere or to a suitable flame andsound quenching muiiler. Within the central opening through thecylindrical stationary contact Iii, and also in register with therestricted throat I4 at the inner end thereof, there is an annularvalve-like member 20 which has a somewhat more restricted throat-likeaperture 2 I through which, under normal operating conditions, the blastof arc extinguishing fluid will be discharged. This annular valve-likemember 2i? is supported for axial movement, with respect to therestricted throat I4, by means of a cage-like support 22 which, as ismore clearly shown in Figure 2, has radial arms 23 that hold itcentrally within the contact I0. This cage-like member 22 also carries acylindrical sleeve 2d which is held in spaced relation with the innerwall of the stationary contact I Il by the radial arms 23, so as to forman auxiliary or Icy-pass conduit 25 through which gases may exhaust whenthe valve-like member 2i! is moved away from the restricted throat ororifice I4 of the stationary contact I6. Mounted within the cylindricalsleeve 2t there is a compression `spring 2G which operates to bias thevalve-like member 2d in a position against the rim of the restrictedthroat It so that upon contact separation, the blast of arcextinguishing fluid will be caused to normally exhaust through thethroat-like aperture 2l thereof. At this point it will be noted that themovable contact Il is provided with a highly refractory arcing tip 27which is resistant to pitting and/or burning away in the event of asustained arcing.

In operation, with the chamber I5 charged with an arc extinguishingfluid, it will be seen that when the moving contact II is moved awayfrom the stationary contact I0, as in interrupting a circuit, any arcdrawn between the respective contact surfaces I2` and|3 orthesecontacts'will be subjected to a'blast of arc extinguishing fluid whichwill normally exhaust centrally throughy the throat-like aperture 2| oftheValve-like member 1`20 'and outwardly to 1 thev atmosphere or amulcr, as abovesuggest'ed. S'However; should the current value of thisarcbe 'ofsucha value as would result'in excessive heating,randa-consequent excessive generation. of ionized gases that might setlup a bloclring'pressure at the `point of contact separation which wouldinterfere ..with 'the free flow 4of cool arc extinguishing fluid throughthev arc, the annular valve-l-ikermember 20 Vwill bemoved .upwardly inresponse to this excessive pressure andthus permit-thisexcessive gaspressure to escape outwardly therearound and to l the atmosphere ormuiler through .the annular auxiliary orfby-pass conduit`25.` Undernormal operating conditions it is anticipated'that thearc extinguishing.fluid'will be 'maintained 'in the' chamber l5 at a pressure somewherebetween 80 andv 100 pounds per square inch, and the spring 2li-will beso arranged and designed as to permit a valve opening movement of theannular valvelike member 20 whenever the pressure atv the restrictedthroat I4 of the stationary contact I0 approachesto Within 50 to 75 percent of the pressurevalue normally maintained within the chamber l5.However, these values may vary under diierent conditions of operation.Inran actual test,v with contacts constructed -as 'here illustrated, itwas found possible, with thevalve member 20 set to respond at a pressureof from 40to V60 pounds-per square inch, to interrupt a current of 4000amperes at 15000 volts within one-half a cycle'withV an air pressure of80'pounds, whereas without the annular valve member, an air pressure of160 `pounds per square inch was required to obtain a comparableperformance at this currentvand voltage. Therefore, it is apparent thatby controlling the exhaust of hot gases from the arcing zone to theatmosphere or muffler, under conditions responsive to the current valuesof the are, a considerable saving in the pressure and quantity of thearc extinguishing :duid results.

Reference is now made to Figures y4 vand 5 of the/drawing,l wherein theinvention vis shown as embodied in a circuit breaker of the so-calledtransverse .blast type. In circuit breakers of this latter type, thecooperating contacts are lgenerally arranged to separate and draw'anyarc established therebetween within a relatively narrow arc chute whichares'outwardly so as to permit a rapid vexhaust and cooling of the iluidblast and arc generated gases. In these figuresl ofthe drawingy astationary contact 28, with which a movable contact 29 is adapted tocooperate, are shown as Varranged to engage and disengage each otherwithin a chamber or arc chute forming housing.' 30. The movable contact29 is of bladelike'conguration,l andl the stationary contact 28 carriesa plurality of yielding contact viingers v3l that engage the oppositesides of the movable contact-29. The stationary Contact 28, with itsyielding-contact fingers 3 I is xed within the chamber of'arc chuteforming housing 30 and opposite thereto the housing 30 has a relativelysmall opening-32 through whichA the'moving contact 29.may travel inmoving into and out of circuit making engagement with the yieldingcontact fingers 3| of thestationary contact28. Immediatelyv above the.rpath ofrtravel of themoving contactf29there is--a .fluid directingconduit 33 through which -a blast of arc-extinguishing iluid maybedischarged into the cl'iarnber.v or :arc chute iforming'fhousing 30transversely to the path `of any: arc that-may be established between'the moving contact 29 andthe yielding. contact' v`lingers .31 f of the.stationary. contacts. Dlrectly.oppos'ite Ito thereon'- duitf 33 the.Varc .chuteiforming housingz: ls= flared outwardly, as'a.t134,wsofas toprovide fontherapl`d exhaust.A of has passed through. thefpathofanynarc'establi'shed f between :the :..contacts 'L18-land; 29 i. LTo'`:accelerate the :breaking-tup. of :anys persister-ritirare, the :daredportion 534. of i thef'arc Achute forming housing 30. `is also'generallyLprovided .with:.a: plurality 'of lspaced Vand radiallyextending :baffle forming-.- members 5:35 which operate. tobreak .up thearc intowsrnallerA segmentsaandifthus provide fora moreleicientcoolingzof, the'hot'zarczgeneratede'gases.k'Arranged.outwardlyzf-beyondf theiiiared portioniu` oftheibameformingmembersl withinizthe housingiSU,.theresisearconduit or muler 36intotwhich .thel cooled @gases iare.flclischarged` and inaliy exhausted;towtheratmosphere: `iThis: arrangement, vas .sof farv described, iswel1' v:known: and understoodnbyf those fskilled in.the.-.art,;and whileit is capable"oninterrupt-ingecircuits athig-h voltages .and'scurrentvalues, J it iris :open-:.toithe objection that its:current'interruptingcapacity is 'limited to a4 relatively.: narrowrangeiofs'c-urrent values. This` diculty is 'believed to be;duef.tothefact thatv the hot gas; coniiningi:housing-:ElliA .makes no allowancesfor 1 variations x in..` gas wprcssuresl which `result fromzthe.interruption .ofaicircuit .at

diierent currentvalues.V .'Inaccordancez-wlthjthc present invention,this: is: overcome bygproviding the arc;.chuteaformingirhousingtallfwithi .faxmeans that will relieve the: arcachutaiiorr'thecchamber thus formed` about the;V arcing ,'.zone betweenthe separating contacts, of :.any; back :pressure ,that might interferewith the vfree andseectiveflow. vof the arc extinguishing iiuidV throughanyarc .which may be drawn between the; stationary contact 28 and themoving contact;29v ininterrupting areircuit. Thisfmeanaas here4show.n,imay be` in the form'of ari-auxiliary vent-or exhaustA outlet 3'lthat will permit theescape'ofv arc generated'gases from the arochuteatthe point ofgcontact separation whenevera back-pressure, vinA excess ofthat whichV Would'preventf-an :effective-flow ofthe arc extinguishingfluid,focc,urs. Thelauxiliarysvent. orv exhaustoutlet 3T maybelocated inone or bothsides of` the arc, chute forminghousing. 30 anchas is moreVclearly shownyin-Figure 5. of the drawing, these auxiliary-vents orexhaust outletsi37 are provided with pressure responsivevalve .members38that are,yieldinglyzffbiased v4into sealing-` relation with:thezauxiliary ventsr.or-exhaust-` outletss. 3 "l, 4by meansv ofisprings39. .-Preferablyf these vents or exhaustoutlets 3`l are'located; closelyadjacentthe point of-contact separation where the-highest gas pressuresareY initially generated. The-.vents or exhaust. outlets -31 are shownfas vdisposed -in the sides of-,thefarc formingfhousing adjacent-theinner ends of thexbaiflev formngfmembers where an accumulation. .ofiihotf. gasesfmight ;1 eiectively set-up; .an back; pressure: that wouldinterfere with, if ,not entirelystop, the How of, the arc extinguishinggases throughl thefchamberorarc chuteforming housing 30. `It isbelieved.:.that ;the,4 operation of this embodiment` oithe inventionwill -be yclearly understoodv from thel 'operationr abovel described inconnection fwith the embodiment of the invention shown in Figure .1.Therefore,"it-appears only. necessary towhere add: that .the springs1139,'

whichwoperate` .tofseat .the twovalvemembers 38' within;the;.auxiliary 1. ventzori exhaustuoutletsll 31,.

the 1 arc 'exting-uishlng fi'luidcafter 'uit herev shown' as disposedone at each side of the arc chute forming housing 39, may be calibratedor designed so as to permit a response of their respectivevalve members38 at different pressure values and, as a result, the Yarc extinguishingcharacteristics ofthe arrangement shown may be rendered eiective toextinguishan arc established between the separating contacts 28 and 23overa Widerrange of current values. i While I have described andillustrated Yspeciiic forms vofthe invention, I desire to have itunderstood that the invention is not limited to the specificarrangements disclosed,l but may be einbodied in other waysthat willsuggest themselves to persons skilled in the art and all such changes ascome within the scope of the appended claims are-tobe considered as partof vthis invention.

Having thus described my invention, what I claim and desireto secure byLetters Patent is- 1. In a uid .blast arc extinguishing circuit breaker,the combination-of a contact enclosing chamber adapted to maintain aiiuid under pressure having an exhaust outlet at one end, a stationarycontact of cylindrical configuration extending into said chamber andforming a continuation of said exhaust outlet through which a liiuidunder pressure within said chamber flow to said exhaust outlet, saidcylindrical contact having its inner end formed to provide an openannular contact surface, .a cooperating :3:7

axially `movable contact having a cooperating contact surface adapted toengage the annular contact surface of said cylindrical contact and-close the opening therethrough, an annular valvelike member disposedwithin and in back of the annular contact surface of said cylindricalcon'- tact having a restricted centrally disposed opening through whicha blast of arc extinguishing uid may flow when said contacts are movedout of engagement* with each other, a cylindrical sleeve forl supportingsaid movable valve-like member centrally in spaced relation with theinner walls of the cylindrical contact and forming an outer annularpassageway leading to the exhaust outlet of said Contact enclosingchamber, and means for yieldinglymaintaining said movable valve-likemember in position where a blast of arc extinguishing fluid will benormally directed through its central opening and permitting movementthereof in the event oi a predetermined arc generated gas pressure toallow the generated gases 'to' flow -aroundl the outside thereof andthrough said annular passageway to the exhaust outlet of said chamber.

2. In a fluid blast `arc extinguishing circuit breaker, the combinationof a contact enclosing chamber adapted to maintain a fluid underpressure having an exhaust outlet at its end, a stationary cylindricalContact mounted within and forming a continuation of the exhaustoutletoi said chamber through which a fluid under pressure within saidchamber may flow to said exhaust outlet, said cylindrical contact havingits inner end formed to provide a truncated conical contact surface, acooperating axially movable contact having a conical contact surfaceadapted to engage-the truncated conical contact vsurface of saidcylindrical contact'and close the opening therethrough, a movablevalve-like member disposedcentrally within said cylindrical contacthaving 'a centrally disposed and. restricted openlng through which ablast of arc extinguishing uid. may flow when said contacts are movedout ofv engagement with each other, means for supporting said movablevalve-like member centrally in spaced relation-with the inner walls ofthe cyl l Contact, and spring means for yieldirigly maintaining saidmovable valve-like member in a position with respect to the truncatedconical contact surface o said cylindrical contact where a blast of arcextinguishing fluid will be normally directed through its centralopening and permitting movement thereof in the event of an abnormal backpressure clue to arc generated gases which will allow said generatedgases to flow around the outside thereof and to said exhaust inlet.

3. In a fluid blast arc extinguishing circuit breaker, the combinationof, a substantially cylindrical contact forming member having an annularcontact surface at its end and a passageway extending centrallytherethrough ior the exhaust oi an arc extinguishing fluid, a secondcontact member adapted to engage said annular contact surface andoperating to close the passageway through saidl cylindrical contact whensaid contacts are in circuit making engagement with each other, apressure confining chamber surrounding said contacts at their point ciseparation adapted to be charged with an arc extinguishing iluid mediumunder pressure, said cylindrical contact being mounted in a wall oi saidchamber and forming an exhaust conduit 'for said arc extinguishingfluid, a passageway dividing means disposed within said cylindricalContact and forming an outer auxiliary passageway therethrough, and apressure responsive valve means cooperating with said passagewaydividing means operating to prevent a now of said arc extinguishr; ingfluid through said auxiliary passageway under normal arcing conditionsand permitting said arc extinguishing iiuid to exhaust through saidauxiliary passageway under abnormal arcing conditions.

4. In a iiuid blast arc extinguishing circuit breaker, the combinationof a substantially cylindrical stationary Contact forming member havingan annular Contact surface at its end and a passageway extendingcentrally therethrough for the exhaust of an arc extinguishing fluid, amovable contact adapted to engage said annular contact surface andsubstantially close the passageway through said cylindrical stationarycontact when said contacts are in circuit making engagement with eachother, a pressure confining chamber surrcunding said contacts at theirpoint of separation adapted to be charged with an arc extinguishingiluid medium under pressure which will exhaust therefrom to extinguishany arc established between said contacts when they separate to open acircuit, said cylindrical stationary contact being mounted in a wall ofsaid chamber and forming an exhaust conduit for said arc extinguishinguid, a cylindrical partition forming means disposed within saidcylindrical contact and forming an annular auxiliary passageway therein,a pressure responsive valve means cooperating with said cylindricalpassageway dividing means operating to prevent a flow of said arcextinguishing iiuid through said outer annular passageway under normalarclng conditions and permitting said arc extinguishing uid to exhaustthrough said annular passageway under abnormal arcing conditions, saidpressure responsive valve means being adapted and arranged to operateand open said auxiliary passageway at a pressure below that which wouldmaintain a blocking pressure oi ionized gases sufficient to prevent anextinction of the arc by a flow of said arc extinguishingk fluid throughsaid cylindrical contact.

5. n a fluid blast arc extinguishing circuit breaker, the combination ofa substantially cylindrical contact having an annular contact surface atone end and a fluid blast exhaust passageway extending centrallytherethrough, a movable contact adapted to move axially with respect tosaid cylindrical contact and close the fluid blast exhaust passagewaythrough said cylindrical contact when said contacts are in circuitestablishing engagement with each other, a chamber surrounding saidcontacts from which an arc extinguishing fluid under pressure mayexhaust through said cylindrical contact to extinguish an arcestablished between said contacts when said contacts separate, meansforming an annular concentrically arranged vent passageway within thefluid blast exhaust passageway through said cylindrical contact, anaxially movable valve member having a centrally located throat-likeopening for the passage of fluid under pressure from said chamber uponseparation of said contacts, said annular valve member being positionedto normally close said annular vent passageway, and spring means formaintaining said annular valve member in its vent passageway closingposition and adapted to permit axial movement of said annular valvemember to open said vent passageway for the escape of ionized gasesgenerated by an arc between said contacts at a pressure below that whichwould establish an exhaust blocking pressure within the throat-likeaperture of said valve member.

6. In a iluid blast arc extinguishing circuit breaker, the combinationof a substantially cylindrical contact having an annular contact surfaceat one end and a fluid blast exhaust passageway extending centrallytherethrough, a movable contact adapted to move axially with respect tosaid cylindrical contact and close the fluid blast exhaust passagewaythrough said cylindrical contact when said contacts are in circuitestablishing engagement with each other, a chamber surrounding saidcontacts from which an arc extinguishing fluid under pressure mayexhaust through said cylindrical contact to extinguish an arcestablished between said contacts when said contacts separate, meansforming an annular concentrically arranged vent passageway within theiluid blast exhaust passageway through said cylindrical contact, andaxially movable valve member having a centrally located throat-likeopening for the passage of fluid under pressure from said chamber uponseparation of said contacts, said annular valve member being positionedto normally close said annular vent passageway, and spring means formaintaining said annular valve member in its vent passageway closingposition and adapted to permit axial movement of said annular valvemember to open said vent passageway for the escape of ionized gasesgenerated by an are between said contacts at a pressure substantiallycorresponding to the pressure of the arc extinguishing fluid flowingbetween said contacts, whereby a blocking of the flow of arcextinguishing fluid between said separating contacts due to any backpressure at said throat-like opening will be avoided.

7, In a fluid blast arc extinguishing circuit breaker, the combinationof a contact enclosing chamber adapted to maintain a fluid underpressure having an exhaust outlet at one end, a cylindrical contactmember mounted within and having its central opening communicating withthe exhaust outlet of said chamber through which a fluid under pressurewithin said chamber may ilow to said exhaust outlet, said cylindricalcontact having its inner end formed to provide an annular contactsurface, a cooperating movable contact having a contact surface adaptedto engage the annular contact surface of said cylindrical contact memberand close the central opening therethrough, an annular valve memberdisposed centrally within said cylindrical contact having its centralopening disposed to form a restricted passageway through which a blastof arc extinguishing fluid may flow when said contacts are moved out ofengagement with each other, means for supporting said valve membercentrally in spaced relation with the inner walls of said cylindricalcontact member, and means for yieldingly maintaining said valve memberin a position with respect to the annular contact surface of saidcylindrical contact member, where a blast of arc extinguishing fluidwill be normally directed through its central opening, but permitting anoperation movement thereof, which will allow arc generated gases to flowaround it and to said exhaust inlet in the event of an abnormal gaspressure due to arcing between said contacts.

ARNOLD E. BROCK.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,944,403 Clerc Jan. 23, 19342,063,173 Lange Dec. 8, 1936 2,084,885 Biermanns i June 22, 19372,367,934 Flurscheim Jan. 23, 1945 2,380,817 Woolard July 31, 19452,399,412 Webb Apr. 30, 1946

